Lignocellulosic material is primarily composed of cellulose, hemicellulose and lignin and provides an attractive platform for generating alternative energy and chemical sources to fossil fuels. The material is available in large amounts and can be converted into sugars which again can be converted into valuable fermentation products, such as biofuel and organic acids.
Producing fermentation products from lignocellulosic material is known in the art and generally includes the steps of pretreatment, hydrolysis, fermentation, and optionally recovery of the fermentation products.
During the hydrolysis, which may comprise the steps of liquefaction, pre-saccharification and/or saccharification, cellulose present in the lignocellulosic material is partly (typically 30 to 95%, dependable on enzyme activity and hydrolysis conditions) converted into reducing sugars by cellulolytic enzymes. The hydrolysis typically takes place during a process lasting 6 to 168 hours (see Kumar, S., Chem. Eng. Technol. 32 (2009), 517-526) under elevated temperatures of 45 to 70° C. and non-sterile conditions. Commonly, the sugars are then converted into valuable fermentation products, such as ethanol and succinic acid, by microorganisms, like yeast.
Succinic acid is a well-known four-carbon organic acid that has high value, since it can be used as a precursor for many important industrial chemicals and consumer products. Currently, succinic acid is produced petrochemically from butane through maleic anhydride. However, much attention has recently been focused on the microbiological production of succinic acid using microorganisms as an alternative to chemical synthesis.
In recent years, largely in response to uncertain fuel supply and efforts to reduce carbon dioxide emissions, production of ethanol from renewable biomass resources is becoming extremely important from the viewpoint of the global environment. Bioethanol is seen as a good fuel alternative, because the source crops can be grown renewably and in most climates around the world. In addition, the use of bioethanol is generally CO2 neutral.
In recent years, the concept of the biorefinery has emerged. In the biorefinery concept biomass conversion processes and technology to produce a variety of products including fuels, power, chemicals and feed for cattle are integrated. This way advantage of the natural differences in the chemical and structural composition of the biomass feed stocks is taken. Careful management and utilization of materials, products and wastes are desirable, making the biorefinery concept a clear example of industrial symbiosis. By producing multiple products and integrating waste treatment, biorefineries can maximize the values derived from biomass feed stocks and turn biomass processing into real opportunities.
Optimization of processes performed within biorefineries and the overall design of biorefineries are crucial tools to increase efficiency of biorefineries and reduce their overall costs.
It is therefore desirable to include new and innovative concepts, designs and process configurations aimed at maximizing the output of biorefineries and reducing their overall costs.